The behavioral response of dairy cows to different shock energies delivered during virtual fencing training.

The uptake of virtual fencing (VF) technologies to manage grazing dairy cattle is increasing, but little empirical evidence exists to support acceptable thresholds for the electric shock delivered by these systems. This study quantified the behavioral responses of dairy cows to 4 shock energy levels delivered by the Halter VF system. Forty early-lactation multiparous dairy cows, naïve to VF, were studied in 5 groups of 8 animals. Within each group, cows were randomly allocated to receive one of 4 shock energies (0.1, 0.2, 0.3, or 0.45 J) via a collar-mounted VF unit. Behavioral responses to shock were recorded and classified using a 6-point reaction score: (1) stop, pause, or no response with no steps taken; (2) fewer than 3 steps taken away from the VF; (3) more than 3 steps taken at a normal walking pace; (4) more than 3 steps taken at a fast walking pace and or head shake; (5) move away at a trotting pace; and (6) jump, vocalization, or 360-degree turn. Linear mixed models were used to assess the effects of shock energy, group, and individual cow on behavioral responses. Most reactions (84%) were classified as scores 1 to 3. Shock energy was not associated with reaction score, the number of shocks received, or the time taken to resume grazing within the 0.1 to 0.45 J range studied. Individual cow accounted for 46% of the variation in behavioral response and 34% of the variation in latency to resume grazing. Individual cow characteristics were more influential than shock energy in determining behavioral responses to shock, reinforcing the importance of delivering the lowest effective stimulus for an individual cow in VF systems, without exceeding tested energy thresholds.